Signaling system



Nov. 2,1926. 1,605,010

' J. S. STONE I S IGNALING SYSTEM Filed Nov. 23, 1923 4 Sheets-Sheet l 0%*"mff"m n, f me fnV GCT -95 l i01- l n FZ l l a je f f IQIH'E f f T kal-:n

c. ATTORNEY Nov. 2 1926.

J. S. STONE SIGNALING SYSTEM J Filed Nov. 2 5, 1923 4 Sheets-Sgeet 2 Xia. u

T F'./5 lm/4 y l N VEN TOR C W ATTORNEY Nov. 2 1926.

J. s. 'STONE SIGNALING SYSTEM Filed Nov. 23, 1923 4 Sheets-Sheet 5 A Troie/ve y Nov. 2 1926.

J. S. STONE SIGNALING SYSTEM Filed Nov. 23. 1925 4 Sheets-Sheet 4 INVENTOR J 630126 Style@ ATTORNEY bien. 22, i926.

istanti JOHN STONE STONE, OF SAN DIEG, CALFGRNIA, ASSGNOR UJG-AMERICAN TELE- PHOLI'E AND TELEGRAEl-I COMPANY, A CQBPORATION OF' NEW" YORK.

SIGNALING SYSTEM.

Application filed November A principal object of my invention is to provide apparatus and method for multiplex signal transmission with carrier currents on wire circuits. Another object of my invention is to eii'ect a carrier current wire transmission through an artificial line in which the wave lengths are short distances and Vto secure selectivity by tapping this artificial line at points properly distanced in relationv to the wave lengths. 'these and various other objects ofr my in vention will be made apparent in the folhming specification and claims taken with the aerompanying` drawings, in which 1 have disclosed a-limited number of specific embodiments of the invention by way `of eXample. At will be understood that the invelr tion is defined in the appended claims and that the following specification relates particularly to the examples disclosed.

Referring to the drawings, Figure l a diagram of a two-wire system embodying my invention and having shunt-connected transformers, Fig. la is a diagram of a system with only a ysingle conductor and having series-connected transformers, Fist. 2 shows two transmitters or receivers or oth connected to the line in conjugate relation, Figs. 3, l and 5 show other connections to the line for the conjugate relationship, Figs. G, 7, S, 9, l() and 1l are diagrams illustrat ing various other embodiments of the invention, Figs. l2, 13, 14 and 15 are diagrams for modifications, Fig. 1G is a 'diagram of an impedance equalizing device, Fig.` 17 shows a selective shunt whose purpose will be explained presently, Fig. 18 shows a terminal station on a transmission line adapted for duplex` operation', Figs. 19, 20, 2l and-22 i0 show arrangements in which twodevices A and A, are both adapted for transmitting and receiving in both directions, Figs. 23 to 2G show systems in which A transmits and receives in both directions, while A, transmits andreceives only on one side and Figs. 2T, 9.8 and 29 are diagrams illustrating certain relations of phase andwave length.

Referring to Fig. l, a long two-conductor transmission line is indicated bythe refer- "G ence. characters a1, "ci, CZ, CZ. From b, b to c, c a short length of artificial lineis interposed. Let the `impedance looking to the leftat ZJ, or to the right at c, be zo. lt willsimplify the design if this impedance is a pure resistance and to make it such, the adjustable 2S, 1923. Serial No. 676,623.

series resistance and reactance elements are` interposed as shown in Fig. l. Let the characteristic resistance of the artificial line Z9, b, c, c be e). vAcross the points and liliewise across the points c, c connect the shunt impedance el, whose value is determined by the equation 1 l l (l Z1 o Z1 v With this condition, the impedance looking out from the artilicialyline at the points 7), and likewise at the points c, c `will be equal to .el and waves traveling along the 'artificial line either way will pass beyond the points n, a or Z), without reflection at those, points.

The artihcial' line l), b, c, c will be smooth,

or of such finely divided elements, that it can'be regarded as practically smooth.A The general formula for thecharacteristic impedance of such Va line is where, per unit of lengt-h, Gr: is the shunt conducta-nce, Gis the shunt capacity, R is the series resistance', L is the series inductance, pis 2W times the frequency, and vl is r ln the present case, let the artificial line be so constructed that its shunt conductance and its -`series resistance are negligible. Accordingly, the formula becomes Vpoints j', f.

Consi -l the system in reiation to waves of a given length A. `Walves of this length traveling alongv the artrcial line will ex Since there are ilo perience an angular retardation between theto (7) and (4) to (7') are exhibited points e and as given by the formula:

Let the retardation of the device for waves of length )t be represented by the same character 0. ln the following equations g is an integer. Four cases may be considered.

(a) Let the interval c, 7" be adjusted so En this case waves coming over the line -from the right and tapped oft by the branches at e and f will arrive at the device A in the same phase, and hence there will be full reception from the iight. On the other hand, waves generated at A will be put on the lines so that those put on the line at e and traveling to the right will arrive at in the same phase as those put on at and accordingly there will be full transmission to the right.

(b) Let the interval between e, f be adjusted sothat diggs-6 (5) In this case there will be full transmission to and reception from the left.

(c) Let the interval between e and 7 be Consider a train of waves coming in from the right. With this adjustment, they will arrive at the device A over the respective branches e and in opposite phase, so that there will be Zero reception from the right. On the other hand, for waves generated at A they will be put on the line at e and f so that those going to the right from e will arrive at f in exactly opposite phase to those put on at f, and there will be zero transmission to the right.

In this case there will be zero reception from the left and zero transmission to the left.

The foregoing equations 1i, 5,6 and 7 express the relations involved in angular measure. Tn terms of lengths the corresponding equations are as follows:

tm) e'i The relations expressed by equations (4) graphically in' Fig. 27. When the point determined by Z (in terms of A) and 6 as coordinates is found to be located on one of the inclined lines of the diagram, then the condition of zero or full transmission to or reception from the right or left will be as indicated by the associated legends. Furthermore, if a point is near such a line, the corresponding condition will be `approximated accordingly.

For transmission `from A in Fig. 1, there will be current and potential nodes and loops between b and c. Assume an origin at the middle point of e, f, where @0:0. There are two cases to be considered. In the following equations (8) and (9), g is an iiiteger as before, but it may be negative as well as positive.

(e) Let l e a l .TJ-(2Q+1 E There will be a potential node and a current loop at any point satisfying equation (8).

(7) Let Y At any point a; satisfying equation (9),

there will be a current node and a. potential loop.

The relations of the foregoing equations (8) and (9) are shown graphically for Fig. l in Fig. 28. With m (in terms of and 6 as coordinates, the point determined ac.- cordingly on Fig. 28 will show by its proximity to one of the inclined lines of the diagram what will be the nearest approach to 1 the condition of node or loop at the corresponding point of the artificial line.

Instead of putting the impedance al across the line as iii Fig. 1, it may be put in series with the line, in which case the condition to be satislied is Zo-harz@ (lo) This will take the place of equation (1). The structural arrangement is shown in Fig. 16.

In Fig. 1 and in all the following figures, for the sake of simplicity and consistency. all the transformer coils shown are assumed to be poled in the same direction, and when 'were very large,y in. Fig. la they should be very small compared with al. The direc tional properties of Fig. lEL are the same as 'for F ig.` l and the foregoing paragraphs (a), (b), (c) and (d) all apply without change. However, the conditions e and ,1" will be reversed, so that where there is a potential node on Fig. 1, there will be a current node onFig. 1Q, etc. The relations lor Fig. la areshown graphically in Fig. 29.

Fig. 2 shows a section. ot' a grounded linel constructed in accordance with the same principles as Fig'` 1. Let be a potential node between e and rIhe device A, counected at this point. will be unadected by the currents generated by the transmitter A. On the other hand, if there is a transmitter at A, its eitect ona receiver at A will be null. Evidenly the two branches containingv the devices A and A, are in conjugate relationship and neither will be affected by currents ot the appropriate frequency that may be generated vby the other. j In case the point is a current node, the branch circuit containing the device A1 may be connected in series as shown in Fig. 3.

Referring to Fig. 4, suppose that both theA point c, and f1 are potential nodes with respect to currents from the transmitter A. A transmitting system similar to that for A may be associated with the points el and ,f1 and the transmitter A1. The branches 1, 2 containing` the device A, and 3, 4 containing the device Al, are in conjugate relationship.

In Fig. 5 the principle involved is similar to that ot Fig. 4 except that while A is connected through shunt branches, A, is connected in series branches, and the connection points e, andA f1 are current nodes instead oi' potent-ialgnodes as in Fig. 4.

In Figs. 4 and 5, it is comparatively un important sov far as the conjugacy of the receiver branches is concerned, what the impedances ot' the branches at c, and f,V may be. It vwe make the impedances of these branches in Fig. 4 to be very large compared to .el and those in Fig. 5 very small compared to el, we may placethese branches at potential loops instead ofnodes in Fig. 4 and at current loops instead ofnodes in Fig. 5, and ob .ain conjugacy between the branches ccntaining A and A1, respectively, by means ci a suitable relation between the phase retarders 0 and 19,.

Referringto Fig. 6, the distance e, f is and the` retardation given by the phase shifter is mined by referring these values to 27 that the device A gives full transmission to the right and has full reception from the right, but it gives zero transmission to the It may at once be deter- In Fig. 7 'the device A., is shown series connected, instead of shunt connected as' in Fig. 6, and the conjugate relationship sub# sistsfor Aand A, in Fig. Z as in Fig. 6.

As explained for 6Fig, Sshows the device A connected in such a way that there is full transmission to and reception from the right, but zero transmission to and rcception fromthe lett'. Clearly, any number of branches such as e, and f, can be placed on the lett without interfering with A or being interfered with by A, and in this way the device A., can be connected with the line through two branches as shown. j

In 9 the device A] is series connected Whereas in Fig. 8 it is shunt connected.k

In Fig. 10, a transmitter T and a receiver i R are Shown in separate branches both connected alike to the line at the points c and f. With the distance e, f equal to 4 and with the phase shitters giving, al retardation ol 2 there will be lull transmission tothe right from the transmitter T and full reception from'` the lett to the receiver It. This shows how independent directional properties may be given to a transmitter and receiver connected at the saine points e andy' on the line.

Fig'. 11 shows ythe correspondirrg.` arrangement with seriesy connected branches instead of shunt` connectedV branches.

In the organizations ot F 4 and 5, the points of connection el and f, both lie between the points-e and In Figs. S and 9, the points e1 and f1 both lie to one side oi the points@ and f; In Figs. 1() and 1-1, the points el and f1 are respectively` coincident with the points @and j?. Figs. 12, 13, 14 and 15 illustrate other special relations which may exist between the points of at* tachment e, f, e] and It will often be desirable that wavesot a different frequency from, that intended for the devices Al, such as. in Fig. 1, shall be readily transmitted over the line from one side to the other without encountering much, if any, impedance at the artificial linel itself. For this purpose a simple anti-'resonant branch between the points Z) and c may,` be employed as in Fig. 17. Theiloop circuit with inductance and capacity in parallel is made-` of negligible resistance` and with a small value tor the ratioAL/C. Itiistuneol to the particular frequency intended for the device, A and accordingly functions practically as it the branch betiveen o and 0 were open for currents ot that frequency, but it atlords a low impedance path tor currents ot substantially different frequencies.

ln some cases it Will be desirable to end the line at one side oi the artificial line l; c. In this case an impedance e() must be interposed to prevent reflections back into the line o c. The proper arrangement` is shown in Fig. 18.

Sonie speeilic niodilications are shown in Figs. 19 to 2G which Will noiv be described. In vieu' oi the principles that have been eX- plained and Vwith the dimensions indicated by the legends on the drawings, it vvill be seen that in each of Figs. i9 to 22 both devices A and ,ill transmit and receive in both directions, but cach is tree troni interference by the other.

in Figs. 23 to QG, inclusive, with the dimensions indicatedby the associated legends, A1 transmits and receives in bolli directions, ivhile transmits and receives only onthe right.

ll'lithin the principles that have been explained, We have here a more flexible system than a mere pair ot conjugate circuits, t'oi We. have means by which either one or both of the conjugate circuits may be given directional properties either as to transmission or reception, and these directional properties ot any one ot the transii'iitters or ifeceivers may be made ditl'erent trom that ot any one ot the other transmitters or receivers.

When We have 'toA deal With a band ot i'iequencies and not ivith a single frequency, the circuits shown ivill not Igive strict conjug'aey tor all the frequencies involved but only tor the medial frequency ot the band, except in the special case when ([:Q For this reason there ivill be a certain advantagije in having' compact circuits Which involve values ot li and L1 between Zero and a.

Moreover, since the rate ot change ot potential and current with distances near a node is very much more rapid than near a loop, the circuits which secure coiijugacy by placing;` bridged branches at .loops oi2 potential and series branches at loops ot current Will be advantageous, when the Width ot the band is a factor, as compared with circuits which depend upon placing` the bridged branches at potential nodes and the series branches at current nodes.

l claim:

l. il. transmission line and branch circuits connected therewith in conjugate relationship, said line and branches comprisingv means to give directional properties along the line in and out ot said branches.

2. A multiplex transmission system comprising a line, a station trom which the line extends both Ways, a length oi: articial line interposed in said line at said station, and tivo translating devices operatively connected with said artificial line, one ot said devices being` connected at tivo places, the points et connection ot said devices beingplaced to rive directional selectivity at the articular' intended operating` frequency ot syste the il. il.. transmission system comprisinga line, a station trom which the line extends both Ways, a length ot artiiicial line interposed' in said line at said station, and a translating device operatively connected with said artiticial line at two places spaced along` said artilicial line to give directional selectivity at the particular intended operating frequency ot the system.

Li. A transmission system comprising' a line and a length oi artificial line serially connected therewith, an auxiliary impedance element associated with said line and artiticial'line at their junction point to equalthe impedance both ways, and a translating; device operatively connected with said artificial line at tivo places spaced along said artificial line to give directional selectivity at the particular intendedV operating vtreqiien/cy ot the system.

A. u'iultiplex transmission system comprisinc; a line., a length oil artificial line serially connected therewith. and two translating devices operatively connected with said artiiicial line, one ot' said devices being connected at tivo places spaced alone' said' artificial line to lcive directional selectivity lil.

at the particular intended operating` frequency oit the system.

A multiplex transmission system comprising,v a line, a station 'from which the line extends both ways, a length ot artificial line interposel in said line at said station, and tivo translating devices operatively connected with said artificial line, at least one oi" them being connected at tivo places spaced along said articial line to give'directional selectivity tor the associated translating device at the particular intended operating trequency of the system.

7; A transmission system comprising` a line and a length ot artiticial line serially connected therewith, means at the junction point to equalize the impedanccs ot the line and artincial line, and a translatingdevice operatively connected vvith said artificial line at tivo points spaced along said art-iiicial line to give directional selectivity at the particular intended operating trequency of the system.

In testimony whereof l have signed my name to this speciiication this llth day of November, 1923.

JOHN STONE STONE.

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